Cold Sore While Pregnant: What to Know

Team Peanut
Team Peanutlast month5 min read

Cold sores are usually harmless, but if you get a cold sore while pregnant, it’s often worth checking in with your doctor. Here, we explore why.

Cold Sore While Pregnant

Cold sores in pregnancy are common and often harmless, but it’s natural to worry when you’ve got a baby on board.

Here’s what to know about having a cold sore while pregnant.

In this article: 📝

  • What is a cold sore?
  • Why is it common to have cold sores in pregnancy?
  • Are cold sores during pregnancy dangerous?
  • When to worry about cold sores during pregnancy

What is a cold sore?

A cold sore is a tingly, painful red spot near your lip.

In technical terms, it’s a localized flare-up of the Herpes Simplex Virus (specifically HSV 1).

Also known as fever blisters, cold sores are annoying, uncomfortable, and very contagious.

About two-thirds of people have had the virus.

And once you’ve been infected, you carry it for the rest of your life.

The virus can then reactivate at any time, becoming contagious and causing those pesky cold sores all over again.

Fun times.

Cold sores are more likely to break out if you’re stressed, your immune system is weakened, or your normal hormone balance is disrupted.

Sound like anything you know?

Why is it common to have cold sores in pregnancy?

Can pregnancy cause a cold sore flare-up?


A lot of women who’ve had a cold sore before will get another one during pregnancy.

It’s most likely to pop up in the first trimester when your immune system lowers its defenses to stop your body from attacking the little peanut who’s taken up residence in your uterus.

In early pregnancy, your hormones are also at their wildest (just check out this chart of how your hCG levels change).

And while we all wish we could switch off stress during pregnancy, it’s often easier said than done.

So are cold sores common in pregnancy?

Sadly, yes.

When you add all the factors together, it’s a perfect storm.

Are cold sores during pregnancy dangerous?

Most of the time, a cold sore is just annoying and isn’t dangerous for either you or your little one.

If you get advice from your doctor first, they’re usually treatable too.

How do you treat a cold sore while pregnant?

The most common treatment of cold sores is a cream containing acyclovir or docosanol, which are both topical antivirals (i.e., you put them on your skin, and they fight the virus that’s causing your symptoms).

Both of these ingredients are on the table during pregnancy (some studies have shown that acyclovir is a bit safer).

But, because the CDC recommends these treatments for mamas-to-be only if the benefits outweigh the risks, you should ask your doctor or pharmacist before using them.

When to worry about cold sores during pregnancy

It’s also important to know that there are a few scenarios where a cold sore is more concerning for mamas-to-be.

If this is you, it’s best to inform your doctor and get advice about the next steps.

If it’s the first time you’ve ever had a cold sore

A recurring cold sore is an infection that sticks to your lip.

But your first herpes infection can affect your whole body, causing symptoms like fever, swollen gums, swollen lymph nodes, and a rash.

In this case, there’s a greater chance that the virus might cross the placenta to your baby.

If you have a cold sore during your third trimester

If you have a cold sore later in pregnancy, your doctor is more likely to offer you antivirals to clear up the infection before your baby is born.

This is because the same virus that causes cold sores in adults can make newborns very unwell if they catch it during birth or during their first few weeks earthside.

If you have an active (i.e., fresh, open, weeping) cold sore when your baby is born, you’ll have to take some steps to try to avoid passing the virus on.

As always, you should follow the advice of your healthcare team.

They will likely tell you to:

  • Wash your hands after you touch your face.
  • Wash your hands before you pick your baby up.
  • Cover the cold sore (for example, by wearing a clean face mask while feeding or burping your little one).
  • Avoid kissing your baby until after the cold sore has healed.

And mamas, you should also ask anyone with a cold sore who visits your baby to take these same steps or wait a few days before they come over.

Not everyone knows about the risks of cold sores for little ones, so don’t be afraid to stand your ground on this one.

And FYI, the symptoms of a potentially dangerous herpes infection in newborns include:

  • Lethargy
  • Refusing feeds
  • Fever
  • Skin rash, including around the eyes and in the mouth

If you know your baby has been in contact with someone with a cold sore and they develop any of these symptoms, take them to the hospital.

The condition needs to be treated with IV antivirals as soon as possible.

And if you need support along the way, know that your Peanut community is here for you!

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